This invention relates generally to an air distribution unit adapted to be mounted in the ceiling of a room and adapted to diffuse air flowing into the room from an air duct located above the ceiling. More specifically, the invention relates to an air diffuser unit having a normally open fire damper which closes automatically in the case of fire in order to help retard the transmission of heat past the diffuser.
In office buildings or the like, a room typically is constructed with a suspended ceiling located below the structural members of the building. Located between the ceiling and the structural members is a plenum within which air distribution ducts may be mounted. It is desirable to provide a ceiling construction which, in the case of fire, is capable of retarding heat flow from the room through the suspended ceiling to the structural members above. The purpose of such a ceiling construction is to keep the air in the plenum below certain critical temperatures for as long as possible so as to reduce the danger of the structural members being weakened by heat to the point of permanent damage or collapse.
At present, suspended ceilings themselves can be constructed to meet certain fire standards or ratings, namely; those established by Underwriters Laboratories, Inc. In addition, automatically closable fire dampers associated with the duct work for delivering air into the room have been designed to meet U.L. fire ratings. The damper, however, is also associated with an air diffuser unit mounted in the suspended ceiling and, to the best of my knowledge, there has not heretofore existed a diffuser unit which could withstand designated fire tests and thus be fire-rated.